August 9

• August 9, 48 BC
  Dictator of the Roman Republic Julius Caesar defeats Senatorial army under Gnaeus Pompeius in the battle of Pharsalus in central Greece, the decisive battle of Caesar's Civil War
• August 9, 14
  Augustus, the first Emperor of the Roman Empire, dies and his adopted son Tiberius succeeds to the throne
• August 9, 378
  Cavalry of Visigoth, a branch of the nomadic tribes of Germanic peoples, destroys Roman army and kills emperor Valens at battle of Adrianople
• August 9, 910
  King Edward of Wessex, son of Alfred the Great, defeats the Northumbrian Vikings at the Battle of Tettenhall
• August 9, 1378
  Cardinals declare Pope Urban VI lawless, anti-Christian, and devil
• August 9, 1483
  Pope Sixtus IV celebrates the first mass in the Sistine Chapel, chapel in the official residence of the Pope, named in his honor
• August 9, 1805
  Austria joins Britain, Russia, Sweden and the Kingdom of Piedmont-Sardinia in the Third Coalition against Napoleonic France and Spain
• August 9, 1842
  United States-Canada border is defined by Webster–Ashburton Treaty
• August 9, 1855
  Antonio López de Santa Anna resigns for the 11th and the last time as President of Mexico
• August 9, 1896
  Otto Lilienthal, German aerodynamic engineer, makes his last glide when his glider No. 11 is upset by a sudden gust of wind and he is unable to regain control
• August 9, 1936
  American track and field athlete Jesse Owens wins his fourth gold medal at the 1936 Summer Olympics in Berlin, so is called "single-handedly crushing Hitler's myth of Aryan supremacy"
• August 9, 1942
  British arrest Indian nationalist Mohandas Gandhi and the entire Congress Working Committee in Bombay
• August 9, 1945
  Fat Man, an implosion-type atomic bomb with a plutonium core, is dropped on Nagasaki, Japan, killing outright 35,000-40,000 people and thousands more from the effect of burns and radiation sickness during the following months
• August 9, 1965
  Singapore gains independence from Malaysia
• August 9, 1974
  Richard Nixon, the 37th President of the United States, resigns from office as a result of the Watergate Scandal, triggered by break-in at the Democratic National Committee headquarters at the Watergate office complex
• August 9, 2007
  The French global bank BNP Paribas in the United Kingdom blocks withdrawals from three hedge funds heavily committed in subprime mortgages, signaling the beginning of Great Recession